The overwhelming fraction of research on pressure-flow phenomena and pulse transmission in blood vessels presupposes linearity. During the last few decades attempts have been made to take into account the nonlinear terms in the underlying equations. Unmanageable computational difficulties, however, have forced the investigators to retain some of the simplifications, thereby restricting the problems analyzed to vessels with small distortions from the original cylindrical shape. The principal investigators recently developed a method permitting the utilization of the full nonlinear equations, including Navier-Stokes. This removes the restriction that vessel distortion must be small and inaugurates a new phase in vascular research. We propose to apply this new tool to the identification of the mechanism that generates the Korotkoff sound used in auscultatory blood pressure measurement. Large arterial deformation occurs in performing this procedure. The new method of solving the full Navier-Stokes equation will be validated in an in vitro model related to the condition of interest.